Self-service refrigerated case having a defrosting system



Jan. 10, 1950 M. D. M MAsTER SELF-SERVICE REFRIGERATED CASE HAVING A DEFROSTING svs'rsu Filed April 29, 1946 JNVENTOR.

MALCOLM D. MACMASTER A TT'ORA/EY Patented Jan. 10, 1950 SELF-SERVICE REFRIGERATED CASE HAVING A DEFROSTING SYSTEM Malcolm D. MacMaster, Woodside, Pa assignor to C. V. Hill & Company, Inc., Trenton, N. 1., a corporation of New Jersey Application April 29, 1946, Serial No. 665,912

18 Claims. (CI. 62-2) My invention relates to self-service display cases and particularly to refrigerated self-service display cases adapted for use in the storage and display of frozen foods or other products.

Self-service display cases are constructed so that they are open at the top during normal usage to enable customers to reach into the case and help themselves to the articles they wish to purchase. When such cases are refrigerat- I ed, moist air from the atmosphere above the open top of the display space tends to diffuse or flow downward into contact with the articles and the portions of the fixture which are cooled by the refrigerating elements. In my Patent No.

2,447,759 and in the patent to Caulk et al. No. 2,382,937 means are provided for overcoming this tendency by circulating air upward about the articles on display and skimmin ofi the warm moist air at the top of the display space. The air containing moisture is then passed over the refrigerating elements so that it will be cooled and deposit its moisture on the refrigerating elements before it actually comes into contact with the articles on display.

In accordance with the present invention additional means are provided for shielding the articles on display from the atmosphere outside the display case whereby frozen foods may be maintained at a temperature below F. and preferably at temperatures of from '0" F. to -l0 F. to preserve them while on display. The condensation of moisture from air coming in contact with the goods takes place very rapidly at such low temperatures and unless the air is first effectively dried the moisture freezes as it condenses, causing the articles to be coated with a film of ice so that they stick together and may even freeze into a solid mass so that they cannot be removed from the display case by the customer. Ice also forms rapidly on the coils and fins of refrigerating elements maintained at such'low temperatures so that their efiiciency decreases and the ice may build up suiliciently to restrict the circulation of air within the display space.

It is also desirable to have a transparent window or panel in the front of self-service display cases but when the refrigerated space is maintained at the low temperatures required for preserving frozen foods the window tends to become fogged very rapidly due to condensation of moisture on the window and as a result the window becomes unsightly and substantially 2 never been provided with a display window heretofore so far as I am aware.

In accordance with the present invention these further problems incident to the use of self service cases in the preservationand display of frozen food products are overcome and novel constructions are provided in which the products are maintained at temperatures sutllciently low to preserve frozen foods and in a substantially dry condition so that the accumulation of frost or ice-on the articles being displayed and on the adjacent portions of the hit-- ture is reduced or prevented. This is accomplished by establishing a rapidly flowing curtain of air above the articles on display and between the articles and the atmosphere above the display space'so that warm moist air is positively removed to the refrigerating elements prior to passage into contact with the articles on display. Defrosting of the refrigerating element is also effected in such a manner that the equipment is operated at high efficiency and the tendency for the glass of display windows of the fixture to become fogged during operation is materally reduced.

The principal object of my invention is to provide a novel type of self-service refrigerated display case adapted for the storage and display of frozen foods.

Another object of my invention is to reduce the condensation of moisture and the formation of frost or ice on the articles being displayed.

A further object of my invention is to provide an improved method and means for the defrosting of refrigerating elements employed in selfservice refrigerated cases operating at temper atures below freezing.

Another object of my invention is to provide a novel type of air circulation within a self-service refrigerated display case whereby the condensation of moisture and the formation of ice on articles or surfaces within the display case is .substantially eliminated.

These and other objects and features of my invention will appear in the following description thereof in which reference is made to the accompanying drawing.

The single figure of the drawing is a view partly in vertical section and partlyin perspective, i1- lustrating a typical form of a self-service refrigerateddisplay case embodying my invention.

In that form of my invention chosen for purposes of illustration in the drawing, the display case is provided with a. rear wall 2, a. bottom l.

opaque. For this reason frozen food cases have 68 and a lower front wall 6, each of which is suitably 3 insulated to reduce heat transfer therethrough. The end wall 8 of the case is also insulated and an insulating glass pane It extends from one end wall to the other above the lower front wall 6 to provide a window through which the articles on display may be seen readily. At the same time ,the display case is open at the top, as indicated at I2, so that customers may reach into the display space indicated at H to remove the articles they wish to purchase.

As shown, the articles are supported on a metal or other heat conducting bottom member 16 which extends from a point spaced rearwardly from the lower front wall 8 to a point which is spaced from the vertical rear wall 2 of the case. A baille member 18 extends vertically from the rear of the article support l6 and cooperates with the rear wall 2 to form an air conducting passage 20 within which the refrigerating coils 22 and the fins 24 are located. A glass panel 26 extends up ward from the front edge of the article support l6 and is spaced from the multiple glass panes in to provide a vertically extending air passage 26 between the glass panel 26 and the multiple glass panes I 0. A deflector 30 extends rearwardly above the upper edge or the glass panel 26 and is mounted on the top of the multiple glass panes ill so that air flowing upward in the passage 28 is di-, rected rearwardly and horizontally across the d18- play space adjacent to the top thereof.

A top meniber 32 is mounted on the upper edge of the rear wa l 2 and extends forwardly over the rear portion of the display space II and a baille member 34 projects downwardly from the top 32 so that air flowing horizontally across the top of the display space will pass beneath the bailie 34 to flow downward over the coils 22 and fins 24 which constitute the refrigerating elements of the construction. The fan or blower 36 is located in the space 38 beneath the article support l6 and above the insulated bottom 4 of the case and is driven by a motor 46.

With this construction an air circuit is provided through which air flows at a relatively high velocity so that it passes forwardly in the chamber 38 from the blower 36 to the lower end of the passage 28 between the glass panel 26 and the multiple glass panes Ill. The air flows upward through the passage 28 to the deflector 30 which directs the air rearwardly so that it is projected horizontally across the top of the display space II. The air then passes beneath bame 3i and flows downwardly over the refrigerating elements in passage 20. Within this passage the air is cooled to a low temperature and its moisture is deposited on the coils 22 and flns 24 and it is dried to such an extent that it will not thereafter deposit moisture on the articles being displayed on coming in contact therewith. The air issuing from the lower end or the passage 26 returns to the blower 36 in chamber 38 to be recirculated.

A portion of the air circulated by the blower 26 passes upward from chamber 38 into the display space It through slots or other openings 42 in the article support l6 so that the articles will be eifectively cooled. Wire partitions H are preferably employed for separating different articles and the slots 42 may be located adjacent the partitions so that they will not be covered by the articles on display and uniform air circulation and cooling of the articles is assured.

The blower 36 is operated at a speed sufllcient to maintain a rapid flow of the air thus circulated and as a result a curtain of refrigerated air extending across the top of the display space is pro- 4 d" cod and maintained. The velocity of flow of the air forming the curtain thus produced is preferably not less than about feet per minute and may be as high as 600 feet per minute as it issues from beneath the deflector 30. The air thus forms a curtain which effectively shields the articles on display from the warm moist air above the display space without obstructing access to the articles being preserved. The flow of air is sufliciently rapid to form a positive barrier to the flow of moist air downward into contact with the articles on display. Any air from the atmosphere above the case is forcibl picked up and carried by the air curtain directly to the refrigerating elements and is there cooled to a low temperature, preferably about 10 F. so that its moisture is deposited on the coils and fins and does not come in contact with the articles being displayed.

With this construction frozen foods may be maintained readily available for removal by the customers and yet the condensation and freezing Of moisture onto the articles does not take place. The articles can be removed readily by the customer without difficulties due to freezing and sticking of the articles to each other or to the surfaces on which they rest is substantially eliminated. At the same time they are attractively displayed and are clearly visible to the customers through the window in the front of the case.

In order to maintain the refrigerating elements operating at a high efflciency the coils and fins must necessarily be defrosted frequently. During such periods a hot liquid, preferably compressed refrigerant, passing to the usual condenser is circulated through the pipe 45 past valve 48 and to the coils 22, to melt the ice which has accumulated on the coils and fins. At the same time the valve 50 in line 52 leading from the expansion valve (notshown) to the coil 22 is closed to cut on the supply of expanding refrigerant. Liquid and flakes of ice dripping from the coils 22 during the defrosting cycle are caught by a trough 54 and are conducted to a drain not shown.

During the defrosting cycle the temperature must necessarily rise to above 32 F. to melt the ice on the coils and fins and therefore the temperature of the air adjacent the coils and fins is raised substantially above that of the body of air in the display space M and the chamber 38. In order to prevent mingling of this warm air from adjacent the coil with the cold air in the display space during the defrosting cycle, the blower is rendered inoperative by breaking the motor ciredit at switch 56. Furthermore, the ballle 34 which extends downward from the top 32 cooperates with the insulated rear wall 2 to form a chamber 56 above the coil which traps warm moist air rising from the heated coil during the defrosting cycle. Therefore, little if any warm air will flow inward above the vertically extending baille l8 to the display space It. Moreover, since the blower 36 is not operated during the defrosting cycle the warm moist air from the coil does not flow downward into contact with the surfaces in the bottom of the case and does not circulate over or cause moisture to condense upon the glass panel 26 or the multiple glass panes H). For this reason there is little or no fogging of the window in the front of the display case as a result of the defrosting operation. In order further to prevent moist air from flowing downward in the space 28 between the glass panel 26 and the multiple glass panes it during the defrosting period a small fan 59 is positioned to produce a slight movement of airupward in through the channel2l even during the defrosting period.

In the preferreh form of my invention illustrated, the defrosting cycle is initiated by timing means to insure defrosting of the coils and fins at predetermined intervals. For this purpose the timing mechanism 60 is arranged to actuate switch 56 to control the electrical circuit including the solenoids 62 and 64 associated with valves ll and 50 respectively so that the valve 48 is opened and the valve 50 is closed at predetermined intervals and at the same time the motor actuating circuit is broken. At such times the flow of expanding refrigerant to the coils 22 is cut off and the hot refrigerant from the condenser is passed to the coils to melt the ice thereon. Pressure actuated means such as a bellows 66 or the like are also connected to the switch 56 through the bell crank '8 or other suitable means so that when the pressure of the heated refrigerant rises on conclusion of the defrosting operation and because of the reduced loss of heat to the melting ice, the pressure actuatedmeans operate to return switch 56 to its normal operating position. The solenoids 62 and N are then deenergized permitting valve 48 to close and valve 50 to open whereas the motor actuating circuit is again closed to start the blower 36 operating again.

At the conclusion of the defrosting cycle the blower 36 is therefore started again to circulate air downward over the coils and fins to which the refrigerant is then being supplied. At this time the air adjacent to the coils and fins which was heated during the defrosting cycle deposits its moisture on the recooled coils and fins and on the lower portion of the vertical bailie It so that little if any warm moist air flows forward and upward through the air passage 28 to cause fogging of the glass panel 26 and the multiple glass panes It. Furthermore, the warm air trapped in the chamber 58 above the coil is cooled by the circulating air and it is carried downward from the chamber 58 to the coils 22 and its moisture is deposited on the coils and does not fiow into contact with the articles being displayed and does not result in fogging of the windows through which the articles on display are observed.

In order to illuminate the articles on display so that they may be presented in an attractive manner, a light 69 is mounted 'on the front edge of the top 32 adjacent to the. downwardly extending hood III which serves as a light shield and reflecd theremovaloficefromthe'coilsandflns. Furthermore little if any moist air is permitted to come into contact with the glass of the windows in the, front of the display case so that fogging of these windows does not take. place even during and subsequent to the defrosting cycle.

The'preservation of the articles at the desired 2 low temperature without the condensation of moisture or the formation of ice thereon is due primarily to the horizontally directed curtain of air which flows at relatively high speed across the top of the display space so as to pick up and carry with it any warm moist' air which may tend to flow or diffuse down toward the articles in the display space M or which may be carried downward by movements of customers as they reach into the display space. Such moist air is picked up by the air curtain and carried directly to the coils and fins of the refrigerating elements' and as a result its moisture is deposited on the refrigerating elements and only cooled air substantially devoid of moisture comes into contact with the articles on display and the adjacent surfaces of the display case.

While I have illustrated and described a proferred form of'my invention it will be understood that numerous changes and modifications may be made in the form, construction and arrangement of the elements and in the mechanism employed for controlling the operation thereof. In view thereof it should be understood that the form of my invention shown in the drawing and herein described is intended to be illustrative only. and is not intended to limit the scope of my invention.

I claim:

1. A self-service refrigerated display case comprising a display space which is thermally insulated about its bottom and side walls but open at the top for access to customers, anarticle support spaced from said bottom and having opposite edges thereof spaced from opposite side walls of the case, baiiles extending upward adjacent said opposite edges of the article support and spaced from said opposite side walls of the case, said bailles terminating below the upper edges of said opposite side walls and cooperating with tor. A glass panel 12 extends from the hood ll y to the baflle 34 beneath the light 68 and cooperates maintained at a temperature sufliciently high to prevent the condensation of moisture and the formation of ice on the hood 10 as the rapidly fiowing curtain of cold air passes beneath the hood to the refrigerating elements. At the same time the heat from the light 68 does not raise the temperature of the air in contact withthe articles on display.

In the construction described frdzen foods are presented and displayed in an attractive manner and in an open-top, self-service refrigerated display case so that they are readily available to the customers. The .condensation of moisture on the articles and the formation of ice and sticking of the articles to each other is therefore prevented. Moreover, the refrigerating elements are maintained at a high efliciency of operation by frequent. defrosting. whereas the defrosting cycle is said side walls and article support to define an air circulating duct extending beneath said article support and having its opposite ends open and located at substantially the same level but below the upper edges of said opposite side walls of the case, refrigerating means in said -duct, means for positively circulating air through said duct, and means located adjacent the upper edge of one of said opposite side walls for directing air horizontally'across the upper portion of said display space from one end of said air circulating duct to the other below the open top of the display space.

' 2. A self-service refrigerated display case for frozen food products having a display space therein which is thermally insulated about the bottom and side walls but openat the top for access to customers, an article support spaced from said bottom, means forming an air circulating duct extending about said article support and terminating at its opposite ends in openings located adjacent but below the upper edges of the side walls of said display space, refrigerating means in said duct, and means for positively circulating air through said duct and across the upper portion of said display space from one end of said duct to the other to pronot prolonged more than is necessary to insure dues a shielding barrier of air traveling at a velocity of at least '100 feet per minute extending across but below the open top of the display space.

3. A self-service refrigerated display case comprising a display space thermally insulated at its bottom and about its front, back and end walls but open at the top for access to customers; an article support spaced from the bottom of said space, means forming air ducts located adjacent the front and rear walls of said space and extending fromwpoints adjacent but below the upper edges of said walls to points beneath said article support, means for positively circulating air downward through the duct adjacent said rear wall, forward within the space beneath said article support and upward through the duct adjacent said front wall, means for directing air adjacent the rear wall, and means for refrigerating the air thus circulated.

4. A self-service refrigerated display case comprising a display space thermally insulated at its bottom and about its front, back and end walls but open at the top for access to OHS-1 tomers, an article support spaced from the bottom of said space, means forming air ducts located adjacent thevfront and rear walls of said space and extending from points adjacent but below the upper edges of said walls to points beneath said article support, means for positively circulating air downward through the duct adjacent said rear wall, forward within the space beneath said article support and upward through the duct adjacent said front wall, means for directing air horizontally across the upper por tion of said display space adjacent but'below the open top thereof and from the upper end of the duct adjacent the front wall to the upper end of the duct adjacent the rear wall, and means located within therear duct for refrigerating air thus circulated. 7

5. A self-service refrigerated display case comprising a display space thermally insulated at its bottom and about its front, back and end walls but open at the top for access to customers, an article support spaced from the bottom of said space, means forming air ducts located adjacent the front and rear walls of said space and extending from points adjacent but below the upper edges of said walls to points beneath said-article support, means for positively air-- culating air downward through the duct adja cent said rear wall, forward within the'space beneath said article support and upward through the duct adjacent said front wall, means for directing air horizontally across the upper portion of said display space from the upper end of the duct adjacent the front wall to the upper end of the duct adjacent the rear wall, means for refrigerating the air thus circulated, means for defrosting said refrigerating means, and means for rendering said air circulating means inactive while said refrigerating means is being defrosted.

3 6. A self-service refrigerated display case comprising a display space thermally insulated at its bottom and about its front, back and end walls but open at :the top for access to customers, an article support spaced from the bottom of said space, means forming air ducts located adjacent ing from points adjacent but below the upper edges of said walls to points beneath said article support, means for positively circulating air downward through the duct adjacent said rear wall, forward within the space beneath said article support and upward through the duct adjacent said front wall, means for directing air horizontally across the upper portion ofsaid display space from the upper end of the duct adjacent the front wall to the upper end of the duct adjacent the rear wall, a refrigerating coil located in the path of flow of the air thus circulated, means for periodically circulating a heating medium through said coil to defrost the coil, and means for rendering said air circulating means inactive while said coil isbeing defrosted.

'l. A self-servicerefrigerated display case comprising a display space thermally insulated at its bottom and about its front, back and end walls but open at the top for access to customers, an article support spaced from the bottom of said space, means forming air ducts located adjacent the front and rear walls of said space and extending from points adjacent but below the upper edges of said walls to points beneath said article support, means for positively circulating air down-ward through the duct adjacent said rear wall, forward wit-in the space beneath said article support and upward through the duct adjacent said'front wall, means for directing air horizontally across the upper portion of said display space from the upper end of the duct adjacent the front wall to the upper end of the duct adjacent the rear wall, a refrigerating coil located in the path of flow of the air thus circulated, means for periodically article support spaced from the bottom of said space, means forming air ducts located adjacent the front and rear walls of said space and extending from points adjacent but below the upper edges of said walls to points beneath said article support, means for positively circulating air downwardthrough the duct adjacent said rear wall, forward within the space beneath said article support and upward through the duct adjacent said front wall, means for directing air horizontally across the upper portion of said display space from the upper end of the duct adjacent the front wall to the upper end of the duct adjacentthe rear wall, a refrigerated coil located in the path of flow of the air thus circulated, means for circulating a volatile refrigerant through said coil to cool the coil, means for circulating heated refrigerant through the coil to 'defrost the coil, time controlled means for initiating the circulation of heated refrigerant through the coil and means responsive to the pressure of the refrigerant in the coil for terminating the circulation of heated refrigerant therethrough.

9. A self-service refrigerated display case comprising a display space thermally insulated at its bottom and about its front, back and end walls but open at the top for access to.customers, an article support spaced from the bottom of said space, means forming air, ducts located adjacent the front and rear walls of said space and extendthe front and rear walls of said space and'ex-j tending from points adjacent but below the upper edges of said walls to points beneath said article support, means for positively circulating air downward through the duct adjacent said rear wall, forward within the space beneath said article support and upward through the duct adjacent said front wall. means for directing air horizontally across the upper portion of said display space adjacent but below the open top thereof and from the upper end of the duct adjacent the front wall to the upper end of the duct adjacent the rear wall, means for refrigerating the air thus circulated, the duct adjacent the front wall being formed in part at least of transparent material through which articles on said article support may be seen from the front of the case.

10. A self-service refrigerated display case comprising a display space thermally insulated at its bottom and about its front, back and end walls but open at the-top for access to customers, an article support spaced from the bottom of said space, means forming air ducts located adjacent the front and rear walls of said space and extending from points adjacent but below the upper edges of said walls to points beneath said article support, means for positively circulating air downward through the duct adjacent said rear wall, forward within the space beneath said article support and upward through the duct adjacent said front wall, means for directing air horizontally across the upper portion of said display space from the upper end of the duct adjacent the front wall to the upper end of the duct adjacent the rear wall, means located within the rear duct for refrigerating air thus circulated, and means located adjacent the upper end of the rear duct for heating exposed surfaces of said case to prevent the accumulation of frost thereon.

11. A self-service refrigerated display case comprising a display space thermally insulated at its bottom and about its front, back and end walls but open at the top for access to customers, an article support spaced from the bottom of said space, means forming air ducts located adjacent the front and rear walls of said space and extending from points adjacent but below the upper edges of said walls to points beneath said article support, means for positively circulating air downward through the duct adjacent said rear wall, forward within the space beneath said article support and upward through the duct adjacent said front wall, means for directing air horizontally across the upper portion of said display space from the upper end of the duct adjacent the front wall to the upper end of the duct adjacent the rear wall, means located within the rear duct for refrigerating air thus circulated, and a light located adjacent and above the rear of said display space and in heat transferring relation to surfaces contacted by air passing to the duct at the rear of the display space to prevent the accumulation of frost on said surfaces.

12. A self-service refrigerated display case comprising a display space thermally insulated at its bottom and about its front, back and end walls but open at the top for access to customers, an article support spaced from the bottom of said space, means forming air ducts located adjacent the front and rear walls of said space and extending from points adjacent but below the upper edges of said walls to points beneath said article support. means for positively circulating air downward through the duct adjacent said rear wall,

. forward within the space beneath said article culating air through said duct and across the support and upward through the duct adjacent said front wall, means for directing air horizontally across the upper portion of said display space from the upper end of the duct adjacent the front wall to the upper end of the duct adjacent the rear wall, a refrigerating coil located in the duct at the rear of said display space to cool the air thus circulated, means for circulating a heating medium through said coil to defrost the coil, and an air space located above said coil and out of the path of circulation of said circulating air for receiving warm air rising from the coil during defrosting thereof.

13. The method of maintaining articles at a I temperature below freezing which comprises the steps of circulating air over a refrigerating coil and into contact with said articles, maintaining said coil at a temperature below freezing while circulating said air, pericdicaliysupplying hot refrigerant to said coil for raising the temperature of said coil above freezing to defrost the coil and terminating circulation of air over the coil during the defrosting period and thereafter terminating circulation of the hot refrigerant to the coil and initiating circulation of air over the coil in response to an increase in pressure of the refrigerant in said coil.

14. A self-service refrigerated display case comprising a display space which is thermally insulated about its bottom and side walls but open at the top for access to customers, an article support spaced from said bottom and having opposite positively circulating air through said duct, means located adjacent the upper edge of one of said opposite side walls for directing air horizontally across the upper portion of said display space from one end of said air circulating duct to the other below the open top of the display space, means for periodically circulating a heating medium through said coil to defrost the coil, time controlled means for initiating the circulation of said heating medium through said coil, and pressure responsive means for terminating the circulation of said heating medium through said coil.

15. A self-service refrigerated display case for frozen food products having a display space therein which is thermally insulated about the bottom and side walls but open at the top for access to customers, an article'support spaced from said bottom, means forming an air circulating duct extending about said article support and terminating at its opposite ends in openings located adjacent but below the upper edges of the side walls of said display space, refrigerating means in said duct, means for positively cirupper portion of said display space from'o'ne end of said duct to the other to produce a shielding barrier of air traveling at a velocity of at least feet per minute extending across but below the open top or the display space. means for periodically circulating a heating medium through said coil to defrost the coii, time con-r means forming that portion of the air duct adjacent the front wall of said space comprises spaced transparent members through which articles display in said space may be viewed.

' mm; no; or; heating medium through said 17. A self-service refrigerated display case of V the character defined in claim 1, wherein means are provided for defrosting the refrigerating means and additional means are provided for rendering said air circulating means inactive while said refrigerating means is being defrosted.

Number Name Date 1,397,392 Amend Nov. 15, 1921 1,907,680 Strass May 9, 1933 1,940,515 Bundling Dec. 19, 1933 2,200,502 Johnson -May 14, 1940 2,257,247 Starr Sept. 30, 1941 2,262,104 Lambrecht Nov. 11, 1941 2,281,770 Hoesel May 5, 1942 2,421,314 Brinkoeter May 27,1947

refrigerating means to defrost the same and means are also provided'for rendering said air circulating means inactive while the refrigerating means is being defrosted.

- MAICOLM D. MAOMASTER.

aarnnnnoas crrnn The following references are of record in the file of this patent:

UNITED STATES pa'mn'rs 

